1. Field of the Invention
The present invention is related to a multiband antenna for mobile communication, particularly to a coplanar coupled-fed multiband antenna for mobile communication.
2. Description of the Related Art
With the great development of wireless communication, various wireless communication technologies and products are progressing and appearing constantly. Various mobile phones appear consequently and the original dual-band operation of the mobile phone is improved to multiple-band operation to satisfy the demand for the mobile phones with more communication bands. It is a great challenge for the conventional planar inverted-F antenna to use single resonance path to realize GSM850/900 operation in the lower band with a limited space. For example, Taiwan Patent Publication No. 490,884 of “Dual-band inverted-F patch antenna and the radiating metal sheet” disclosed an inverted-F patch antenna to realize the dual-band operation. However, the lower band of such an antenna can cover GSM900 operation only.
To solve the said problem, we provide a design of the coupled-fed antenna for multiband mobile communication device to cover GSM850 (824˜894 MHz), GSM900 (890˜960 MHz), DCS (1710˜1880 MHz), PCS (1850˜1990 MHz) and UMTS (1920˜2170 MHz) operations. This design is a single antenna having a dual-resonance characteristic to realize the wideband operation, and the lower band is obtained by mainly using a coplanar coupling feed to reduce the inductive reactance of the antenna, thereby the former single resonance mode in the lower band can achieve the dual-resonance characteristic to cover GSM850/900 operation. Besides, the structure of the antenna is simple and easily printed or etched on a surface of the dielectric substrate, thereby making the antenna fabrication at low cost. Therefore, the antenna of the present invention is applicable for mobile communication devices.